Select the option which is not correct with respect to enzyme action :
a)
A non−competitive inhibitor binds the enzyme at a site distinct from that which binds the
substance
b)
Malonate is a competitive inhibitor of succinic dehydrogenase.
c)
Substrate binds with enzyme at its active site.
d)
Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by
malonate.
Correct answer is option 'D'. Can you explain this answer?

Question

Select the option which is not correct with respect to enzyme action :

a)
A non−competitive inhibitor binds the enzyme at a site distinct from that which binds the
substance
b)
Malonate is a competitive inhibitor of succinic dehydrogenase.
c)
Substrate binds with enzyme at its active site.
d)
Addition of lot of succinate does not reverse the inhibition of succinic dehydrogenase by
malonate.

Correct answer is option 'D'. Can you explain this answer?

Answer

The reduction of activity of succinate dehydrogenase by malonate is an example of competitive inhibition. Competitive inhibition is a reversible inhibition where inhibitor competes with the normal substrate for the active site of enzyme. A competitive inhibitor is usually similar to the normal substrate and, therefore, fits into the active site of an enzyme and binds with it. The enzyme, now cannot act upon the substrate and reaction products are not formed. Hence, action of an enzyme may be reduced or inhibited. Since a competitive inhibitor occupies the site only temporarily, the enzyme action is not permanently affected. Thus, addition of a lot of succinate can reverse the inhibition of succinic dehydrogenase by malonate.

Answer

Answer

Explanation:
Malonate as a Competitive Inhibitor:
- Malonate is a competitive inhibitor of succinic dehydrogenase which means it competes with the substrate (succinate) for the active site of the enzyme.
- It binds to the active site of the enzyme, preventing the substrate from binding and inhibiting the enzyme's activity.
Non-competitive Inhibitor:
- A non-competitive inhibitor binds to the enzyme at a site distinct from the active site where the substrate binds.
- It does not compete with the substrate for the active site but instead binds to a different site on the enzyme, causing a conformational change that inhibits enzyme activity.
Substrate Binding to Enzyme:
- Substrate binding to the enzyme occurs at the active site, which is a specific region on the enzyme where the substrate molecule fits perfectly.
- The binding of the substrate to the active site allows the enzyme to catalyze the reaction by lowering the activation energy.
Reversal of Inhibition:
- Addition of a lot of succinate cannot reverse the inhibition of succinic dehydrogenase by malonate because malonate is a competitive inhibitor.
- Competitive inhibitors can be overcome by increasing the concentration of the substrate (succinate) as it will outcompete the inhibitor for binding to the active site of the enzyme.
- However, in this case, adding a lot of succinate will not reverse the inhibition caused by malonate because the inhibitor's binding to the enzyme is reversible and can be overcome by removing the inhibitor from the active site.

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